Method for producing porous molded body, method for producing catalyst for α-olefin dimerization, method for producing α-olefin dimer, porous molded body, and catalyst for α-olefin dimerization

ABSTRACT

Provided is a method of producing a porous molded body, the method including: the step of obtaining a molded body by molding a raw material that contains from 1 part by mass to 100 parts by mass of a bicarbonate compound (A) represented by AHCO3 (wherein, A represents Na or K) and from 0 parts by mass to 99 parts by mass of a compound (B) represented by BnX (wherein, B represents Na or K; X represents CO3, SO4, SiO3, F, Cl, or Br; and n represents an integer of 1 or 2 as determined by the valence of X) (provided that a total amount of (A) and (B) is 100 parts by mass); and the step of obtaining a porous molded body by performing a heat treatment of the molded body in a temperature range of from 100° C. to 500° C. and an atmosphere that contains water vapor in an amount of from 1.0 g/m3 to 750,000 g/m3 and thereby thermally decomposing not less than 90% by mass of the bicarbonate compound (A).

TECHNICAL FIELD

The present invention relates to: a method of producing a porous moldedbody; a method of producing an α-olefin dimerization catalyst; a methodof producing an α-olefin dimer; a porous molded body; and an α-olefindimerization catalyst.

BACKGROUND ART

As monomers for the production of polyolefins, α-olefin dimers typifiedby 4-methyl-1-pentene (including co-dimers; the same applies below) areutilized. Many basic catalysts have been conventionally proposed ascatalysts for the production of corresponding dimers through α-olefindimerization reactions (including co-dimerization reactions; the sameapplies below). Particularly, many catalysts obtained by supporting analkali metal on a carrier containing an anhydrous potassium compound asa main component have been used.

With regard to these catalysts, it has been continuously studied tofurther enhance the activity and the selectivity to a target substance.In addition, since the catalyst life is not necessarily sufficient evenwhen the initial activity is high, studies for extending the catalystlife have also been conducted continuously.

Moreover, the activity, the selectivity and the life of catalysts havebeen improved by adjusting the physical properties of anhydrouspotassium compounds and carriers to be used. For example, JapanesePatent Application Laid-Open (JP-A) Nos. S58-114737, H3-42043,H7-222927, 2006-326418 and 2008-149275 as well as U.S. Pat. No.5,081,094 disclose α-olefin dimerization catalysts.

Further, for example, WO 2015/093378 discloses a porous molded body usedas a carrier of an α-olefin dimerization catalyst.

SUMMARY OF THE INVENTION Technical Problem

The present inventors conducted various studies on catalysts typified bythose disclosed in the above-described patent documents. As a result, itwas revealed that, for example, the catalysts disclosed in JP-A Nos.S58-114737, H3-42043, F17-222927, 2006-326418 and 2008-149275 areobserved with certain effects of improvement in terms of activity andselectivity; however, their carriers tend to collapse in long-termreactions, making continuous operation difficult.

In addition, for example, the catalyst using a potassiumbicarbonate-containing carrier disclosed in U.S. Pat. No. 5,081,094 isin a powder form and thus not suitable for industrial production.Moreover, for example, U.S. Pat. No. 5,081,094 discloses that thecarrier may be molded into the form of a pellet or the like; however,since the use of water in molding causes dissolution of potassiumbicarbonate, it is inferred that the catalyst cannot be filled into amolding die smoothly and this makes the physical properties of theresulting molded body non-uniform.

Furthermore, for example, WO 2015/093378 discloses a method of producinga molded body that is porous and has a pore volume adjusted in aspecific range (i.e., a porous molded body) as a molded body to be usedas a carrier of an α-olefin dimerization catalyst. It is disclosedtherein that the use of this molded body as a carrier of an α-olefindimerization catalyst improves the reaction selectivity as compared tothe use of a known catalyst.

For example, in the production of the porous molded body disclosed in WO2015/093378, it is more desirable that the pore size is adjustable. Morespecifically, for example, there is a case where it is demanded toproduce a porous molded body that has a pore size larger than that of aporous molded body obtained by the method disclosed in WO 2015/093378.

In view of the above, an object of the invention is to provide: a porousmolded body that can be used as a carrier of an α-olefin dimerizationcatalyst, the porous molded body having excellent reaction selectivityin an α-olefin dimerization reaction and being adjusted to have a largerpore size; and a method of producing the same.

Another object of the invention is to provide: an α-olefin dimerizationcatalyst using the porous molded body; a method of producing the same;and a method of producing an α-olefin dimer using the catalyst.

Solution to Problem

The present disclosure encompasses the following embodiments.

<1> A method of producing a porous molded body, the method including:

the step of obtaining a molded body by molding a raw material thatcontains from 1 part by mass to 100 parts by mass of a bicarbonatecompound (A) represented by AHCO₃ (wherein, A represents Na or K) andfrom 0 parts by mass to 99 parts by mass of a compound (B) representedby B_(n)X (wherein, B represents Na or K; X represents CO₃, SO₄, SiO₃,F, Cl, or Br; and n represents an integer of 1 or 2 as determined by thevalence of X) (provided that a total amount of (A) and (B) is 100 partsby mass); and

the step of obtaining a porous molded body by performing a heattreatment of the molded body in a temperature range of from 100° C. to500° C. and an atmosphere that contains water vapor in an amount of from1.0 g/m³ to 750,000 g/m³ and thereby thermally decomposing not less than90% by mass of the bicarbonate compound (A).

<2> The method of producing a porous molded body according to <1>,wherein the duration of the heat treatment is from 0.3 hours to 24hours.

<3> The method of producing a porous molded body according to <1> or<2>, wherein the temperature of the heat treatment is in a range of from100° C. to 300° C.

<4> The method of producing a porous molded body according to any one of<1> to <3>, wherein the heat treatment is performed in an atmospherethat contains water vapor in an amount of from 10.0 g/m³ to 750,000g/m³.

<5> The method of producing a porous molded body according to any one of<1> to <4>, wherein not less than 97% by mass of the bicarbonatecompound (A) is thermally decomposed by the heat treatment.

<6> The method of producing a porous molded body according to any one of<1> to <5>, wherein, when a total amount of the bicarbonate compound (A)and the compound (B) in the raw material is 100 parts by mass, theamount of the bicarbonate compound (A) is from 10 parts by mass to 100parts by mass and that of the compound (B) is from 0 parts by mass to 90parts by mass.

<7> The method of producing a porous molded body according to any one of<1> to <6>, wherein the raw material is molded by tableting.

<8> The method of producing a porous molded body according to any one of<1> to <7>, wherein

when the raw material contains the compound (B), a mixture of thebicarbonate compound (A) and the compound (B) has a median diameter(d50) of from 5 μm to 600 μm in terms of volume statistical value, and

when the raw material does not contain the compound (B), the bicarbonatecompound (A) has a median diameter (d50) of from 5 μm to 600 μm in termsof volume statistical value.

<9> The method of producing a porous molded body according to any one of<1> to <8>, wherein a content ratio of particles having a particle sizeof 40 μm or smaller in the raw material is from 3% by mass to 30% bymass.

<10> The method of producing a porous molded body according to any oneof <1> to <9>, wherein the bicarbonate compound (A) is potassiumbicarbonate (KHCO₃).

<11> The method of producing a porous molded body according to any oneof <1> to <10>, wherein the compound (B) is potassium carbonate (K₂CO₃).

<12> The method of producing a porous molded body according to any oneof <1> to <11>, wherein the raw material further contains a graphite(C).

<13> A method of producing an α-olefin dimerization catalyst, the methodincluding:

the step of producing a porous molded body by the method of producing aporous molded body according to any one of <1> to <12>; and

the step of obtaining an α-olefin dimerization catalyst by supporting analkali metal (D) on the porous molded body.

<14> A method of producing an α-olefin dimer, the method including:

the step of producing an α-olefin dimerization catalyst by the method ofproducing an α-olefin dimerization catalyst according to <13>; and

the step of Obtaining an α-olefin dimer by performing a dimerizationreaction of an α-olefin in the presence of the α-olefin dimerizationcatalyst.

<15> A porous molded body including a carbonate compound (A1) that is atleast either one of sodium carbonate (Na₂CO₃) and potassium carbonateK₂CO₃), wherein

pores having a pore diameter in a range of from 0.05 μm to 10 μm have amedian pore size of larger than 0.36 μm but 0.90 μm or smaller,

the pores having a pore diameter in a range of from 0.05 μm to 10 μmhave a volume in a range of from 0.10 mL/g to 0.30 mL/g, and

the porous molded body has a crushing strength of from 1.8 kgf to 8.5kgf.

<16> The porous molded body according to <15>, wherein a content ratioof the carbonate compound (A1) is not less than 70% by mass with respectto a total amount of the porous molded body.

<17> The porous molded body according to <15> or <16>, further includingat least one compound (B1) represented by Na_(n)Y or K_(n)Y (wherein, Yrepresents SO₄, SiO₃, F Cl, or Br; and n represents an integer of 1 or 2as determined by the valence of Y).

<18> The porous molded body according to any one of <15> to <17>,wherein the median pore size is in a range of from 0.40 μm to 0.90 μm.

<19> The porous molded body according to any one of <15> to <18>,wherein the volume of the pores is from 0.20 mL/g to 0.30 mL/g, and thecrushing strength is from 2.2 kgf to 7.0 kgf.

<20> The porous molded body according to any one of <15> to <19>,wherein the carbonate compound (A1) is K₂CO₃.

<21> The porous molded body according to any one of <15> to <20>,further including a graphite (C).

<22> An α-olefin dimerization catalyst, in which an alkali metal (D) issupported on the porous molded body according to any one of <15> to<21>.

Effects of Invention

According to the disclosure, a method of producing a porous molded bodythat can be used as a carrier of an α-olefin dimerization catalyst, theporous molded body having excellent reaction selectivity in an α-olefindimerization reaction and being adjusted to have a larger pore size, isprovided.

Further, according to the disclosure, a method of producing an α-olefindimerization catalyst using the porous molded body and a method ofproducing an α-olefin dimer using the catalyst are provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing the relationships between the pore size andthe log differential pore volume in the porous molded bodies of Examplesand Comparative Example; and

FIG. 2 is a graph showing the relationships between the heat treatmenttime (thermal decomposition time of KHCO₃) and the median pore size ofthe respective porous molded bodies in Examples and Comparative Example.

DETAILED DESCRIPTION OF THE INVENTION Mode for Carrying Out theInvention

In the present specification, those numerical ranges that are expressedwith “to” each denote a range that includes the numerical values statedbefore and after “to” as a lower limit value and an upper limit value,respectively.

In a set of numerical ranges that are stated in a stepwise manner in thepresent specification, the upper limit value or the lower limit value ofa numerical range may be replaced with the upper limit value or thelower limit value of other numerical range. Further, in a numericalrange stated in the present specification, the upper limit value or thelower limit value of the numerical range may be replaced with a valueindicated in Examples.

In the present specification, the unit of crushing strength [kgf] can beconverted into [N] based on a relational expression: 1 kgf=9.8 N.

In the present specification, the term “step” encompasses not onlydiscrete steps but also steps that cannot be clearly distinguished fromother steps, as long as the intended purpose of the step is achieved.

<Method of Producing Porous Molded Body>

The method of producing a porous molded body according to the disclosure(hereinafter, also referred to as “the production method of thedisclosure”) includes:

the step of obtaining a molded body by molding a raw material thatcontains from 1 part by mass to 100 parts by mass of a bicarbonatecompound (A) represented by AHCO₃ (wherein, A represents Na or K) andfrom 0 parts by mass to 99 parts by mass of a compound (B) representedby B_(n)X (wherein, B represents Na or K; X represents CO₃, SO₄, F, Cl,or Br; and n represents an integer of 1 or 2 as determined by thevalence of X) (provided that a total amount of (A) and (B) is 100 partsby mass); and

the step of obtaining a porous molded body by performing a heattreatment of the molded body in a temperature range of from 100° C. to5500° C. and an atmosphere that contains water vapor in an amount offrom 1.0 g/m³ to 750,000 g/m³ and thereby thermally decomposing not lessthan 90% by mass of the bicarbonate compound (A).

By the studies conducted by the inventors, it was discovered that aporous molded body, which is obtained by molding a raw materialcontaining the bicarbonate compound (A) and the compound (B) andsubsequently thermally decomposing not less than 90% by mass of thebicarbonate compound (A) through a heat treatment of the thus obtainedmolded body in a specific temperature range and an atmosphere containinga specific amount of water vapor, not only simply has pores but also isadjusted to have a larger pore size. It was also discovered that thereaction selectivity of an α-olefin dimerization reaction is improvedwhen this porous molded body is applied as a carrier of an α-olefindimerization catalyst.

In other words, according to the production method of the disclosure, aporous molded body that has excellent reaction selectivity in anα-olefin dimerization reaction and can be used as a carrier of anα-olefin dimerization catalyst is obtained.

The reasons why the effects of the disclosure are obtained arespeculated as follows; however, the production method of the disclosureshould not be interpreted restrictively based on the below-describedreasons.

In α-olefin dimerization reactions, there are cases where an α-olefinmultimer is generated by a side reaction and pores of a catalyst areclogged by this multimer. Such clogging of pores is presumed to cause areduction in the reaction selectivity of the α-olefin dimerizationreactions.

According to the disclosure, it is believed that the structure of theporous molded body adjusted to have a larger pore size contributes tosuppression of the generation of an α-olefin multimer in an α-olefindimerization reaction. It is surmised that this inhibits clogging ofpores of a catalyst caused by the multimer (i.e., by-product) and thereaction selectivity of the α-olefin dimerization reaction isconsequently improved.

In the production method of the disclosure, the amount of water vapor inthe water vapor-containing atmosphere during the heat treatment of themolded body is from 1.0 g/m³ to 750,000 g/m³, preferably from 10.0 g/m³to 750,000 g/m³.

When the amount of water vapor is 1.0 g/m³ or greater, a porous moldedbody adjusted to have a larger pore size is more likely to be obtained.In addition, when the amount of water vapor is 1.0 g/m³ or greater, itis likely that the pore volume of the porous molded body is adjusted tobe large as well.

When the amount of water vapor is 750,000 g/m³ or less, excellentproduction suitability is attained.

The lower limit value of the amount of water vapor is preferably 5.0g/m³, more preferably 10.0 g/m³, still more preferably 12.0 g/m³.

The upper limit value of the amount of water vapor is preferably 100,000g/m³, more preferably 10,000 g/m³, still more preferably 1,000 g/m³,particularly preferably 500 g/m³.

It is noted here that the term “bicarbonate compound (A)” used hereinrefers to a compound that is thermally decomposed during a heattreatment of a molded body to generate a gas such as water vapor.

In other words, in the production method of the disclosure, the phrase“an atmosphere that contains water vapor” refers to an atmosphere thatcontains a gas such as water vapor generated by thermal decomposition ofthe bicarbonate compound (A).

In the production method of the disclosure, the temperature at which themolded body is heat-treated (i.e., heat treatment temperature) is from100° C. to 500° C.

When the heat treatment temperature is 100° C. or higher, the thermaldecomposition of the bicarbonate compound (A) is facilitated, so that aporous molded body adjusted to have a larger pore size is more likely tobe obtained. In addition, when the heat treatment temperature is 100° C.or higher, it is likely that the pore volume of the porous molded bodyis adjusted to be large as well.

Moreover, when the heat treatment temperature is 500° C. or lower,excellent production suitability is attained.

The heat treatment temperature is preferably from 100° C. to 400° C.,more preferably from 100° C. to 300° C., still more preferably from 150°C. to 300° C., particularly preferably from 150° C. to 250° C.

In the production method of the disclosure, the duration of the heattreatment of the molded body (i.e., heat treatment time) is preferably0.3 hours or longer.

The term “heat treatment time” used herein refers to a time required forthe bicarbonate compound (A) to be thermally decomposed. The heattreatment may be continuously performed even after the completion of thethermal decomposition of the bicarbonate compound (A).

The heat treatment time is usually longer than the thermal decompositiontime of the bicarbonate compound (A).

A method of determining the thermal decomposition time of thebicarbonate compound (A) will be described below in the section ofExamples.

When the heat treatment time is 0.3 hours or longer, the thermaldecomposition of the bicarbonate compound (A) is facilitated, so that aporous molded body adjusted to have a larger pore size is more likely tobe obtained. In addition, it is likely that the pore volume of theporous molded body is adjusted to be large as well. The heat treatmenttime is more preferably 2 hours or longer from the standpoint of makingit easier to control the heat treatment conditions.

The upper limit of the heat treatment time is not particularlyrestricted; however, it is preferably not longer than 24 hours from thestandpoint of the heat treatment cost.

The heat treatment time is preferably from 0.3 hours to 24 hours, morepreferably from 2 hours to 24 hours. A longer heat treatment time tendsto result in a larger pore size. In other words, the pore size can becontrolled by adjusting the heat treatment conditions.

The details of the heat treatment process will be described below.

The steps of the production method of the disclosure will now bedescribed.

[Step of Obtaining Molded Body]

The step of obtaining a molded body is the step of obtaining a moldedbody by molding a raw material. The term “raw material” used hereinrefers to a raw material of a molded body.

(Raw Material)

The raw material contains from 1 part by mass to 100 parts by mass of abicarbonate compound (A) represented by AHCO₃ (wherein, A represents Naor K), and from 0 parts by mass to 99 parts by mass of a compound (B)represented by B_(n)X (wherein, B represents Na or K; X represents CO₃,SO₄, SiO₃, F, Cl, or Br; and n represents an integer of 1 or 2 asdetermined by the valence of X) (provided that a total amount of (A) and(B) is 100 parts by mass).

The constitution of the raw material encompasses a case where the amountof the compound (B) is 0 parts by mass, i.e., a case where the compound(B) is not contained in the raw material.

The reason for this is because, when the bicarbonate compound (A) isthermally decomposed during the heat treatment of the molded body and agas such as water vapor is generated, pores are formed at those partswhere the gas is generated, whereby a porous molded body adjusted tohave a larger pore size can be obtained.

—Bicarbonate Compound (A)—

The bicarbonate compound (A) is represented by Formula AHCO₃.

In Formula AHCO₃, A represents Na or K. The bicarbonate compound (A)represented by Formula AHCO₃ is a compound that is at least either oneof sodium bicarbonate (NaHCO₃) and potassium bicarbonate (KHCO₃). Whenthe bicarbonate compound (A) contains both sodium bicarbonate (NaHCO₃)and potassium bicarbonate (KHCO₃), the mixing ratio thereof is notparticularly restricted.

The amount of the bicarbonate compound (A) contained in the raw materialis from 1 part by mass to 100 parts by mass, preferably from 10 parts bymass to 100 parts by mass, more preferably from 30 parts by mass to 100parts by mass, still more preferably from 40 parts by mass to 100 partsby mass, particularly preferably from 40 parts by mass to 90 parts bymass, most preferably from 50 parts by mass to 90 parts by mass, withrespect to a total of 100 parts by mass of the bicarbonate compound (A)and the compound (B).

From the standpoint of obtaining a porous molded body adjusted to have alarger pore size, the bicarbonate compound (A) is preferably potassiumbicarbonate (KHCO₃) represented by the above-described Formula wherein Ais K.

—Compound (B)—

The compound (B) is represented by Formula B_(n)X.

In Formula B_(n)X, B represents Na or K; X represents CO₃, SO₄, SiO₃, F,Cl, or Br; and n represents an integer of 1 or 2 as determined by thevalence of X.

In other words, the compound (B) represented by Formula B_(n)X iscarbonate, sulfate, silicate, fluoride, chloride, or bromide of sodiumor potassium. The compound (B) may be any one or more of compoundsrepresented by B_(n)X. When the compound (B) is a mixture of two or moreof such compounds, the mixing ratio thereof is not particularlyrestricted.

The amount of the compound (B) contained in the raw material is from 0parts by mass to 99 parts by mass, preferably from 0 parts by mass to 90parts by mass, more preferably from 0 parts by mass to 70 parts by mass,still more preferably from 0 parts by mass to 60 parts by mass,particularly preferably from 10 parts by mass to 60 parts by mass, mostpreferably from 10 parts by mass to 50 parts by mass, with respect to atotal of 100 parts by mass of the bicarbonate compound (A) and thecompound (B).

When X in Formula B_(n)X is SO₄, SiO₃, F, Cl or Br, the amount of thecompound (B) contained in the raw material is preferably 30 parts bymass or less, more preferably 20 parts by mass or less, still morepreferably 10 parts by mass or less, with respect to a total of 100parts by mass of the bicarbonate compound (A) and the compound (B).

Among the above-described compounds, the compound (B) is preferablypotassium carbonate (K₂CO₃) represented by the above-described Formulawherein B is K, X is CO₃, and n is 2.

(Graphite (C))

The raw material may further contain a graphite (C).

When the raw material further contains the graphite (C) and the rawmaterial containing the graphite (C) is molded by, for example, thebelow-described compression molding (e.g., tableting), the movement of amortar and a pestle is likely to be smooth, so that the density of theresulting molded body is likely to be stable.

The characteristics of the graphite (C) are not particularly restricted,and any graphite may be used as long as it is generally used as alubricant in molding.

Examples of such a graphite (C) that is generally used include graphitesthat have a median diameter (d50) in a range of from 5 μm to 500 μm interms of volume statistical value and a specific surface area in a rangeof from 0.1 m²/g to 300 m²/g as measured by a BET method. The graphite(C) may be a natural graphite or an artificial graphite.

The amount of the graphite (C) to be added to the raw material can beset arbitrarily as long as the molding can be performed.

When the raw material contains the compound (B), the amount of thegraphite (C) to be added to the raw material is preferably from 0.3parts by mass to 10 parts by mass, more preferably from 0.5 parts bymass to 5 parts by mass, with respect to a total of 100 parts by mass ofthe bicarbonate compound (A) and the compound (B).

Meanwhile, when the raw material does not contain the compound (B), theamount of the graphite (C) to be added to the raw material is preferablyfrom 0.3 parts by mass to 10 parts by mass, more preferably from 0.5parts by mass to 5 parts by mass, with respect to 100 parts by mass ofthe bicarbonate compound (A).

When the added amount of the graphite (C) is 10 parts by mass or less,the strength of the resulting molded body is unlikely to be reduced.With the added amount of the graphite (C) being 0.3 parts by mass orgreater, for example, an excessive increase in abrasion between a mortarand a pestle can be suppressed when the raw material is molded bytableting. This allows an apparatus to operate in a favorable manner, sothat the density of the resulting molded body is likely to be stable.

Accordingly, when the added amount of the graphite (C) is in theabove-described range, a molded body can be favorably molded.Consequently, the strength of a porous molded body obtained byheat-treating the molded body is likely to be ensured.

The raw material of the molded body may also contain, as required, acompound other than the above-described bicarbonate compound (A),compound (B) and graphite (C) within a range that does not impair theeffects of the disclosure.

Examples of such other compound include ammonium bicarbonate. When theraw material contains ammonium bicarbonate, the pore volume of theresulting porous molded body can be further increased.

(Characteristics of Raw Material)

When the raw material contains the compound (B), the median diameter(d50) of a mixture of the bicarbonate compound (A) and the compound (B)is preferably from 5 μm to 600 μm, more preferably from 20 μm to 500 μm,still more preferably from 50 μm to 450 μm, particularly preferably from50 μm to 300 μm, in terms of volume statistical value.

When the raw material does not contain the compound (B), the mediandiameter (d50) of the bicarbonate compound (A) is preferably from 5 μmto 600 μm, more preferably from 20 μm to 500 μm, still more preferablyfrom 50 μm to 450 μm, particularly preferably from 50 μm to 300 μm, interms of volume statistical value.

A powder having a median diameter in a range of from 5 μm to 600 μm hasa favorable fluidity and is thus capable of yielding a molded body in astable manner.

The content ratio of particles having a particle size of 40 μm orsmaller in the raw material is preferably from 3% by mass to 30% bymass.

It is generally known that small-sized particles are desired to beremoved because of their poor movement during tableting, and it is thuspreferred to control the content ratio of particles having a particlesize of 40 μm or smaller to be in the above-described range. When thecontent ratio of particles having a particle size of 40 μm or smaller isin the above-described range, the fluidity of the raw material isensured, so that blocking is unlikely to occur and the raw material canbe uniformly and easily loaded at the time of molding the raw material.

It is noted here that the particle size distribution of the bicarbonatecompound (A) and that of the compound (B) may be different as long asthe content ratio of particles having a particle size of 40 μm orsmaller is in a range of from 3% by mass to 30% by mass in the mixtureof the bicarbonate compound (A) and the compound (B).

(Molding of Raw Material)

In the disclosure, a method of molding the raw material is notparticularly restricted and, for example, extrusion molding, compressionmolding, or granulation molding is employed. It is noted here that,since the bicarbonate compound (A) dissolves in water, it is preferrednot to add water to the raw material (i.e., the raw material contains nowater).

Among the above-described molding methods, from the standpoint of thecharacteristics of the raw material, the raw material is moldedpreferably by compression molding, particularly preferably by tableting.

When the raw material is molded by compression molding, the raw materialis usually filled into a mortar serving as a die and compressed with apestle to be molded.

Meanwhile, when the raw material is molded by tableting, since the rawmaterial is uniformly filled into a mortar, a molded body with a smallvariation in density tends to be obtained.

When the raw material is molded by extrusion molding, a molding rawmaterial which is imparted with enough viscosity to maintain its shapeby an addition of a liquid to the raw material is molded through a die.In the case of molding the raw material by extrusion molding, since thebicarbonate compound (A) dissolves in water, it is preferred to use anorganic solvent or the like in which the bicarbonate compound (A) doesnot dissolve.

When the raw material is molded by tableting, the density of theresulting tablet molded body is preferably from 1.6 g/mL to 2.3 g/mL,more preferably from 1.8 g/mL to 2.2 g/mL. The density of the tabletmolded body can be adjusted by controlling the compression strength.

The size and the shape of the molded body are not particularlyrestricted. The shape of the molded body can be selected based on theconditions of a molding apparatus and the like, and the molded body mayassume any of a noodle shape, a cylindrical shape, a convex shape, aring shape, and a spherical shape.

When the raw material is molded by tableting, the shape of the resultingmolded body is preferably a cylindrical shape, a convex shape or a ringshape, and it is more preferably a cylindrical shape from thestandpoints of the ease of molding and the strength.

As a tableting apparatus, any commercially available tableting apparatuscan be used. The tableting apparatus may be of a rotary type or a presstype, and an apparatus of an optimum scale can be selected asappropriate in accordance with the production amount. When the rawmaterial is molded into a cylindrical shape using a tableting apparatus,the resulting molded body usually has a size of from 2 mm to 5 mm indiameter and from 2 mm to 6 mm in height.

When the size of the molded body is in this range, an excessivereduction in the size of the molded body is inhibited, so that anincrease in the number of tableting operations can be suppressed.Consequently, the productivity is improved and the cost can be reduced.

Moreover, with the size of the molded body being in the above-describedrange, when the molded body is heat-treated and subsequently applied asa carrier of an α-olefin dimerization catalyst or the like, the rawmaterial and the product are likely to favorably diffuse in the reactionsystem, and the activity and the selectivity of α-olefin dimerizationreaction are thus likely to be improved.

[Step of Obtaining Porous Molded Body]

The production method of the disclosure includes the step of obtaining aporous molded body by performing a heat treatment of the molded body ina temperature range of from 100° C. to 500° C. and an atmosphere thatcontains water vapor in an amount of from 1.0 g/m³ to 750,000 g/m³(preferably from 10.0 g/m³ to 750,000 g/m³) and thereby thermallydecomposing not less than 90% by mass of the bicarbonate compound (A).

The preferred range of the heat treatment temperature is as describedabove.

In the step of obtaining a porous molded body, the molded body isheat-treated in the above-described temperature range and an atmospherethat contains water vapor in the above-described range, wherebypreferably not less than 97% by mass, more preferably not less than 98%by mass, still more preferably not less than 99% by mass of thebicarbonate compound (A) is thermally decomposed.

The thermal decomposition rate of the bicarbonate compound (A) in theheat treatment of the molded body is adjusted by the amount of watervapor in the water vapor-containing atmosphere, the heat treatmenttemperature, and the heat treatment time. When the heat treatmenttemperature is relatively low, the above-described thermal decompositionrate can be attained by extending the heat treatment time. Bycontrolling the thermal decomposition rate of the bicarbonate compound(A) in the above-described range, a porous molded body adjusted to havea larger pore size is likely to be obtained. In addition, it is likelythat the pore volume of the porous molded body is adjusted to be largeas well. As a result, when the porous molded body is applied as acarrier of an α-olefin dimerization catalyst, the selectivity ofα-olefin dimerization reaction is improved.

In the heat treatment of the molded body, examples of a method ofheat-treating the molded body in an atmosphere that contains water vaporin an amount of from 1.0 g/m³ to 750,000 g/m³ (preferably from 10.0 g/m³to 750,000 g/m³) include a method of performing the heat treatment whileintroducing water vapor to a heat treatment apparatus; a method ofperforming the heat treatment while introducing air (ambient air) to aheat treatment apparatus; a method of performing the heat treatmentusing a heat treatment apparatus having a hermetically closed structure;a method of performing the heat treatment by setting, for example, acrucible in which the molded body is placed and which is subsequentlycovered with a lid, in a heat treatment apparatus; and combinations ofthese methods.

In other words, it is preferred to perform the heat treatment of themolded body in an atmosphere that contains a gas such as water vaporgenerated by thermal decomposition of the bicarbonate compound (A)contained in the molded body, while allowing the generated gas such aswater vapor to remain.

The specifications and the structure of the heat treatment apparatus arenot particularly restricted, and any commonly-used heating furnace,electric furnace, belt furnace, hot-air circulating furnace or the likecan be employed.

A method of determining the amount of water vapor during the heattreatment of the molded body (i.e., the amount of water vapor in thewater vapor-containing atmosphere) will be described below in thesection of Examples.

(Porous Molded Body)

In the production method of the disclosure, the porous molded body ofthe disclosure is obtained through the step of obtaining a molded bodyand the step of obtaining a porous molded body.

The porous molded body of the disclosure contains a carbonate compound(A1) that is at least either one of sodium carbonate (Na₂CO₃) andpotassium carbonate (K₂CO₃).

In the porous molded body, pores having a pore diameter in a range offrom 0.05 μm to 10 μm have a median pore size of larger than 0.36 μm but0.90 μm or smaller and the pores having a pore diameter in a range offrom 0.05 μm to 10 μm have a volume in a range of from 0.10 mL/g to 0.30mL/g, and the porous molded body has a crushing strength of from 1.8 kgfto 8.5 kgf.

The porous molded body contains the carbonate compound (A1) that is atleast either one of sodium carbonate (Na₂CO₃) and potassium carbonate(K₂CO₃).

The carbonate compound (A1) is produced in the porous molded body by thegeneration of a gas such as water vapor caused by thermal decompositionof the bicarbonate compound (A) during the heat treatment of the moldedbody.

When the carbonate compound (A1) is a mixture of sodium carbonate(Na₂CO₃) and potassium carbonate (K₂CO₃), the mixing ratio thereof isnot particularly restricted.

The carbonate compound (A1) is preferably potassium carbonate (K₂CO₃).

The content ratio of the carbonate compound (A1) is preferably not lessthan 70% by mass, more preferably not less than 80% by mass, still morepreferably not less than 90% by mass, with respect to a total amount ofthe porous molded body.

When the compound (B) is contained in the raw material yielding themolded body, the porous molded body may further contain at least onecompound (B1) represented by Formula Na_(n)Y or K_(n)Y (wherein, Yrepresents SO₄, SiO₃, Cl, or Br; and n represents an integer of 1 or 2as determined by the valence of Y). In other words, the compound (B1) issulfide, silicate, fluoride or bromide of sodium or potassium.

The compound (B1) may be any one of compounds represented by FormulaNa_(n)Y or K_(n)Y, or may be a mixture of two or more of such compounds.When the compound (B1) is a mixture of two or more of such compounds,the mixing ratio thereof is not particularly restricted.

When the compound (B1) is contained in the porous molded body, thecontent ratio of the compound (B1) is preferably higher than 0% by massbut 30% by mass or lower, more preferably higher than 0% by mass but 20%by mass or lower, still more preferably higher than 0% by mass but 10%by mass or lower.

When the raw material contains a graphite (C), the porous molded bodymay further contain the graphite (C). The graphite (C) added to the rawmaterial may be oxidized depending on the temperature and the atmospherein the heat treatment of the molded body; however, an arbitrary amountof the graphite (C) added to the raw material may remain in the porousmolded body.

When the graphite (C) is contained in the porous molded body, thecontent ratio thereof is preferably higher than 0% by mass but 10% bymass or lower, more preferably higher than 0% by mass but 5% by mass orlower.

—Median Pore Size—

From the standpoint of improving the reaction selectivity when theporous molded body is applied as a carrier of an α-olefin dimerizationcatalyst, the median pore size of the porous molded body is preferablylarger than 0.36 μm, more preferably 0.40 μm or larger. From thestandpoint of the production suitability, the upper limit value of themedian pore size is preferably 0.90 μm.

The median pore size is defined as a value that is calculated frommeasured sizes of pores having a pore diameter (i.e., pore size) in arange of from 0.05 μm to 10 μm. A method of determining the median poresize will be described below in the section of Examples.

—Pore Volume—

From the standpoint of improving the reaction selectivity when theporous molded body is applied as a carrier of an α-olefin dimerizationcatalyst, the pore volume of the porous molded body is preferably from0.10 mL/g to 0.30 mL/g, more preferably from 0.25 mL/g to 0.30 mL/g,still more preferably from 0.20 mL/g to 0.30 mL/g.

The pore volume can be adjusted by, for example, adjusting the densityof the tablet molded body.

The pore volume is defined as a volume of pores having a pore diameter(i.e., pore size) in a range of from 0.05 μm to 10 μm. A method ofdetermining the pore volume will be described below in the section ofExamples.

—Crushing Strength—

The crushing strength of the porous molded body is preferably not lessthan 1.8 kgf, more preferably not less than 2.2 kgf, still morepreferably not less than 3.0 kgf. From the standpoint of the productionsuitability, the upper limit value of the crushing strength is 8.5 kgfor 7.0 kgf.

The term “crushing strength” used herein represents the strength of theporous molded body in the radial direction. The above-described noodleshape, cylindrical shape, convex shape, ring shape and spherical shapeall have a direction corresponding to the radial direction. When theporous molded body has a shape without a direction corresponding to theradial direction, the strength in the direction having the loweststrength is defined as the crushing strength.

The crushing strength is generally known as a physical property thatrepresents the compressive strength of a granule, and it is usuallydetermined by pressing a single molded body of interest, such as apellet or a tablet, in its barrel direction and measuring the force whenthe molded body is crushed. A test method thereof is prescribed in JISZ8841 (1993) “Granules and Agglomerates—Test Methods for Strength”.

In the production method of the disclosure, after molding the rawmaterial containing the bicarbonate compound (A) and the compound (B),the thus obtained molded body is heat-treated in the above-describedtemperature range and an atmosphere that contains a specific amount ofwater vapor, whereby not less than 90% by mass of the bicarbonatecompound (A) is thermally decomposed. As a result, a porous molded bodyadjusted to have a larger pore size is obtained.

In the prior art, the molded body is heat-treated while forciblyeliminating a gas such as water vapor generated by the thermaldecomposition of the bicarbonate compound (A) so as to prevent retentionof the generated gas. In contrast, in the production method of thedisclosure, the molded body is heat-treated in an atmosphere thatcontains a specific amount of water vapor (i.e., while retaining the gassuch as water vapor generated by the thermal decomposition of thebicarbonate compound (A)). Consequently, a porous molded body adjustedto have a larger pore size is obtained. In addition, it is likely thatthe pore volume of the porous molded body is adjusted to be large aswell. Moreover, the strength of the porous molded body (e.g., crushingstrength in the radial direction) is ensured.

When the porous molded body obtained in this manner is applied as acarrier of an α-olefin dimerization catalyst, the selectivity ofα-olefin dimerization reaction is improved.

The porous molded body obtained by the production method of thedisclosure can be preferably used as a carrier of an α-olefindimerization catalyst, and it may also be used as a catalyst carrierother than a carrier of an α-olefin dimerization catalyst.

<Method of Producing α-Olefin Dimerization Catalyst>

The method of producing an α-olefin dimerization catalyst according tothe disclosure includes: the step of producing a porous molded body bythe above-described method of producing a porous molded body; and thestep of obtaining an α-olefin dimerization catalyst by supporting analkali metal (D) on the porous molded body.

In other words, according to this production method, an α-olefindimerization catalyst having excellent selectivity in an α-olefindimerization reaction can be obtained.

The alkali metal (D) is preferably sodium, potassium, or a mixture ofsodium and potassium.

The term “alkali metal (D)” used herein refers to a non-ionized,zero-valent metal. The alkali metal (D) may contain a component otherthan an alkali metal when the purity of the alkali metal is 90% orhigher. Examples of the component other than an alkali metal include theelements in Group I of the periodic table, such as lithium andpotassium; various oxides and hydroxides; and metal elements other thanthe elements in Group I of the periodic table.

Various methods may be employed as a method of supporting the alkalimetal (D) on a carrier composed of the porous molded body of thedisclosure.

The temperature of a supporting treatment is usually in a range of from150° C. to 400° C. From the standpoint of obtaining a catalyst that isexcellent in catalytic activity, catalyst life and selectivity toα-olefin dimerization products, the temperature of the supportingtreatment is preferably in a range of from 200° C. to 350° C., morepreferably in a range of from 200° C. to 300° C. The atmosphere of thesupporting treatment may be a reducing atmosphere or an inertatmosphere, as long as it is not a moist and oxidizing atmosphere.Taking into consideration the safety and the economic efficiency, thesupporting treatment is preferably performed in a nitrogen atmosphere.

In the supporting treatment, the carrier composed of the porous moldedbody is preferably vibrated, rotated or stirred so as to allow thecarrier to uniformly support the alkali metal (D). The supported alkalimetal (D) is known to induce an exchange reaction with an alkali metalcontained in the carrier when brought into contact with the carrierunder heating.

The content ratio (support ratio) of the alkali metal (D) in theresulting α-olefin dimerization catalyst is usually in a range of from0.5% by mass to 10% by mass, preferably in a range of from 1% by mass to6% by mass, taking a total amount of the alkali metal (D) and thecarrier as 100% by mass.

In this production method, a porous molded body adjusted to have alarger pore size is obtained by the step of producing a porous moldedbody. Since the support ratio of the alkali metal (D) and the catalyticactivity correlate with each other, the porous molded body adjusted tohave a larger pore size can support a greater amount of the alkali metal(D).

In other words, according to this production method, a highly activeα-olefin dimerization catalyst can be obtained. In addition, when anα-olefin dimerization reaction is performed using this catalyst, theselectivity of the α-olefin dimerization reaction is improved.Generally, a higher activity tends to cause an increase in the load onthe carrier and to thereby increase the possibility that collapse of thecatalyst carrier (porous molded body) is facilitated; however, sincestrength (e.g., crushing strength in the radial direction) is ensured inthe porous molded body, it is believed that the α-olefin dimerizationcatalyst is unlikely to collapse.

<Method of Producing α-Olefin Dimer>

The method of producing an α-olefin dimer according to the disclosureincludes: the step of producing an α-olefin dimerization catalyst by theabove-described method of producing an α-olefin dimerization catalyst;and the step of obtaining an α-olefin dimer by performing a dimerizationreaction of an α-olefin in the presence of the α-olefin dimerizationcatalyst.

In other words, according to this production method, since adimerization reaction of an α-olefin is performed in the presence of theα-olefin dimerization catalyst having excellent reaction selectivity, anα-olefin dimer can be obtained with a high yield.

Specific examples of the α-olefin include lower α-olefins, such asethylene, propylene, 1-butene, isobutylene, and 1-pentene. Amongdimerization reactions of these lower α-olefins, the α-olefindimerization catalyst obtained by the production method of thedisclosure is preferably used in the production of 4-methyl-1-pentenethrough dimerization of propylene and the production of3-methyl-1-pentene through co-dimerization of 1-butene and ethylene.

The reaction temperature in the dimerization reaction of the α-olefinusing the α-olefin dimerization catalyst obtained by the productionmethod of the disclosure is usually from 0° C. to 300° C., preferablyfrom 50° C. to 200° C.

Further, the reaction pressure is usually from normal pressure to 19.6MPa (200 kg/cm²-G), preferably in a range of from 1.96 MPa to 14.7 MPa(from 20 kg/cm²-G to 150 kg/cm²-G).

The state of the α-olefin in the dimerization reaction varies dependingon the conditions of the dimerization reaction and the type of theα-olefin; however, the α-olefin may generally assume a liquid-phasestate, a gas-phase state, or a supercritical state.

Among these states, the dimerization reaction is preferably performedwith the α-olefin being in a gas-phase state or a supercritical state.

The dimerization reaction of the α-olefin can be performed in a fixedbed system or a fluidized bed system and, between these systems, thedimerization reaction is preferably performed in a fixed bed system.When the dimerization reaction is performed in a fixed bed system, theliquid hourly space velocity (LHSV) of the α-olefin is usually in arange of from 0.1 hr⁻¹ to 10 hr⁻¹, preferably in a range of from 0.5hr⁻¹ to 5 hr⁻¹.

After the completion of the dimerization reaction, unreacted α-olefinand a product are separated from the resulting mixture in accordancewith a conventional method, and the unreacted α-olefin is circulated andrecycled for the reaction.

EXAMPLES

The invention will now be described concretely by way of Examplesthereof; however, the present invention is not restricted thereto.

[Measurement of Median Diameter (d50)]

Mesh sieves having a mesh size of 850 μm, 500 μm, 300 μm, 212 μm, 100μm, 53 μm or 20 μm were each prepared. Subsequently, in a glove box inwhich nitrogen was circulated, 30 g of a powder of interest was put onthe upper part of each mesh sieve and manually sieved. Thereafter, themass of the powder remaining on each mesh sieve was measured todetermine the median diameter (d50).

[Measurement of Content Ratio of Particles Having Particle Size of 40 μmor Smaller]

In a glove box in which nitrogen was circulated, 30 g of a powder ofinterest was put on the upper part of a mesh sieve having a mesh size of40 μm and manually sieved. The mass of the powder that passed throughthe sieve was measured, and the thus measured value was divided by theinitial amount of 30 g to calculate the content ratio of particleshaving a particle size of 40 μm or smaller.

[Measurement of Thermal Decomposition Rate of Bicarbonate Compound (A)]

Using a differential thermo-gravimetric analyzer (manufactured by RigakuCorporation, model: TG8120), a porous molded body obtained was heated to400° C., and the amount of weight reduction was measured. From therelationship between the content of the bicarbonate compound (A) duringmolding and the thus measured amount of weight reduction, the thermaldecomposition rate was calculated. Stoichiometrically, 1 mole of waterand 1 mole of CO₂ are generated from 2 moles of the bicarbonate compound(A). When the thermal decomposition rate is 100% by mass, since nofurther thermal decomposition takes place, a reduction in weight is notobserved on the differential thermo-gravimetric analyzer.

[Measurement of Pore Volume and Median Pore Size]

The volume of pores having a pore diameter (i.e., pore size) in a rangeof from 0.05 μm to 10 μm was measured by a mercury intrusion methodusing a mercury porosimeter (manufactured by MicroMetrics, Inc., model:AUTO PORE IV). Further, the sizes of pores in this range were measured,and the median pore size was determined from the thus measured values.

[Measurement of Crushing Strength of Porous Molded Body]

Using a digital hardness meter (manufactured by Fujiwara ScientificCompany Co., Ltd., model: KHT-40N), the crushing strength of the porousmolded body in the radial direction (i.e., in the barrel direction ofthe cylindrical molded body) was measured in accordance with the methodprescribed in JIS Z8841 (1993) “Granules and Agglomerates—Test Methodsfor Strength”.

In the principle of the measurement of the crushing strength, acylindrical porous molded body to be measured is placed on a stationarysample table, and a movable pressing surface is lowered from above at aconstant rate and pressed against the cylindrical porous molded body tomeasure the strength when the cylindrical porous molded body is broken.

Example 1

[Production of Porous Molded Body]

As a bicarbonate compound (A) and a compound (B), 60 parts by mass ofpotassium bicarbonate (KHCO₃) (manufactured by Junsei Chemical Co.,Ltd., purity: 99%, catalog No.: 43300-1201) and 40 parts by mass ofK₂CO₃ (purity: 99%, specific surface area measured by BET method: 1.3m²/g, bulk density: 0.46 g/mL), respectively, were mixed to obtain 100parts by mass of a powder mixture. The median diameter (d50) of the thusobtained powder mixture and the content ratio of particles having aparticle size of 40 μm or smaller are shown in Table 1.

It is noted here that the median diameter (d50) of the powder mixtureand the content ratio of particles having a particle size of 40 μm orsmaller are values determined by the above-described respective methods.

The powder mixture in an amount of 100 parts by mass was homogeneouslymixed with 0.9 parts by mass of a graphite (purity: 98%, median diameter(d50): 0.6 μm, specific surface area measured by BET method: 150 m²/g),and the resultant was used as a tableting raw material (i.e., a rawmaterial of a molded body) which was subsequently tableted whilecontrolling the compression strength such that the resulting tabletmolded body had a density of 2.0 g/mL, whereby a tablet molded bodyhaving a cylindrical shape of 3 mm in diameter and 3 mm in height wasobtained. Then, 116 kg of the thus obtained tablet molded body wasplaced in a tray, and the tray was put into a hot-air circulatingfurnace of 4 m³ in capacity without covering the tray with a lid. Thetemperature of the furnace was raised from room temperature (e.g., 25°C.) to 155° C. at a rate of 65° C./h and then maintained for 12 hours,after which the temperature was further raised to 300° C. at a rate of24° C./h and maintained at 300° C. for 1 hour, whereby a heat-treatedmolded body (i.e., porous molded body (1)) was obtained. The thermaldecomposition rate of KHCO₃ was 100% by mass.

In the hot-air circulating furnace, the ambient air was introduced at arate of 60 m³/hr. Since the ambient air had a temperature of 25° C. anda relative humidity of 60%, the water vapor content (i.e., water vaporamount) of the ambient air is calculated to be about 13.9 g/m³.

Since 116 kg of the tablet molded body contained about 69.0 kg of KHCO₃,the amount of water generated by thermal decomposition is calculated tobe about 6.2 kg. Further, the total heating time was 21 hours; however,the heat treatment time (i.e., thermal decomposition time of KHCO₃) wasestimated to be 15.5 hours from the temperature of the molded body.

Based on these values, the average water vapor content during the heattreatment is calculated as follows:

13.9g/m³ + (6.2 × 1, 000g/(60m³/h × 15.5hr) ≈ 20.6g/m³.

The thermal decomposition time of KHCO₃ was specifically determined asfollows.

The change in the molded body temperature was actually measured, and apoint when the molded body temperature reached 100° C., which is thedecomposition temperature of KHCO₃, was judged as the start of thethermal decomposition, while a point when the increase in the moldedbody temperature started to follow the increase in the temperature ofthe drying furnace was judged as the completion of the thermaldecomposition of KHCO₃. Since the thermal decomposition of KHCO₃ is anendothermic reaction, the increase in the molded body temperature wasslower than the increase in the atmospheric temperature during thecontinuation of the thermal decomposition reaction.

Table 1 shows the pore volume, the median pore size and theradial-direction crushing strength of the thus obtained porous moldedbody (1).

[Preparation of α-Olefin Dimerization Catalyst]

After drying 96.5 parts by mass of the porous molded body (1) in anitrogen gas flow at 300° C. for 2 hours, 3.5 parts by mass of sodiumwas added thereto in a nitrogen gas flow, and the resultant was stirredat 280° C. for 3.5 hours to prepare an α-olefin dimerization catalyst(1).

Since no adhesion of the added sodium to its carrying container wasobserved, it was judged that the whole amount of sodium was supported onthe porous molded body. The support ratio in this process was 3.5% bymass.

[Dimerization Reaction of Propylene]

The α-olefin dimerization catalyst (1) in an amount of 4 g, which wasobtained by the above-described preparation method, was added to asingle-tube reactor of 18 mm in diameter, and propylene was continuouslyfed to a catalyst layer at a reactor internal temperature of 140° C., areaction pressure of 9.8 MPa and a propylene flow rate of 4 g/h toperform a synthesis reaction of 4-methyl-1-pentene (hereinafter,abbreviated as “4MP-1”) through dimerization of propylene. The propyleneconversion rate and the 4MP-1 selection rate in the execution of180-hour flow reaction are shown in Table 1.

Example 2

A heat-treated molded body (i.e., porous molded body (2)) was obtainedin the same manner as in Example 1, except that the mixing ratio of thebicarbonate compound (A) and the compound (B) was changed as shown inTable 1, that the amount of the tablet molded body placed in the traywas changed to 11 kg, and that the temperature of the furnace was raisedfrom room temperature (e.g., 25° C.) to 100° C. at a rate of 75° C./hand subsequently further raised to 200° C. at a rate of 10° C./h andthen to 300° C. at a rate of 16.6° C./h before being maintained at 300°C. for 1 hour, and the same operations as in Example 1 were performedthereafter. The results thereof are shown in Table 1.

Since 11 kg of the tablet molded body contained about 8.7 kg of KHCO₃,the amount of water generated by thermal decomposition is calculated tobe about 0.78 kg.

Further, the KHCO₃ decomposition time, namely the heat treatment time,in a total heating time of 18 hours was estimated to be 10.0 hours.Based on these values, the average water vapor content during the heattreatment is calculated as follows:

13.9g/m³ + (0.78 × 1, 000g/(60m³/h × 10.hr) ≈ 15.2g/m³.

Example 3

A tablet molded body in an amount of 5 g, which was obtained in the samemanner as in Example 2, was put into a crucible of 14 cm³ in capacity,and the crucible was covered with a lid and placed in an electricfurnace. The temperature of the furnace was raised from room temperature(e.g., 2555° C.) to 300° C. at a rate of 27° C./h and then maintained at300° C. for 2 hours, whereby a heat-treated molded body (i.e., porousmolded body (3)) was obtained. Table 1 shows the pore volume, the medianpore size and the radial-direction crushing strength of the thusobtained porous molded body (3).

It is noted here that the pore volume, the median pore size and theradial-direction crushing strength of the porous molded body (3) arevalues determined by the above-described respective methods.

Water and carbon dioxide are generated by thermal decomposition of KHCO₃during the heat treatment; however, since the crucible was nothermetically closed, the water vapor content in the crucible wasdetermined as follows, assuming that the atmospheric pressure in thecrucible was maintained at 1 atm.

First, the thermal decomposition time and the thermal decompositiontemperature range of KHCO₃ were estimated in the same manner as inExample 1. The results thereof are shown in Table 1.

Next, assuming that water and carbon dioxide are generated at a volumeratio of 1:1 by thermal decomposition of KHCO₃ during the heat treatment(i.e., during the thermal decomposition), the amount of water “m” (unit:g) is calculated as follows, assuming that: with respect to a totalpressure of 1 atm, water vapor partial pressure (P)=0.5 atm, volume(V)=1 m³=1,000 L, water molecular weight (M)=18 g/mol, ideal gasequation: PV=(m/M)RT (T: absolute temperature (unit: K)).

0.5atm × 1, 000L = m(g)/18(g/mol) × 0.0821atm·L/(mol·K) × Tm(g) = (0.5 × 1, 000 × 18/0.0821)/T = 109622.4/T

By the above equations, the water vapor content is calculated to beabout 294 g/m³ when T=373K (100° C.) and about 210 g/m³ when T=523K(i.e., 250° C.).

Example 4

A heat-treated molded body (i.e., porous molded body (4)) was obtainedin the same manner as in Example 3, except that the heat treatment wasperformed by raising the temperature from room temperature (i.e., 25°C.) to 300° C. at a rate of 60° C./h and then maintaining thetemperature at 300° C. for 2 hours, and the same operations as inExample 3 were performed thereafter. The results thereof are shown inTable 1.

Example 5

A heat-treated molded body (i.e., porous molded body (5)) was obtainedin the same manner as in Example 3, except that the heat treatment wasperformed by raising the temperature from room temperature (i.e., 25°C.) to 300° C. at a rate of 550° C./h and then maintaining thetemperature at 300° C. for 2 hours, and the same operations as inExample 3 were performed thereafter. The results thereof are shown inTable 1.

Example 6

A heat-treated molded body (i.e., porous molded body (6)) was obtainedin the same manner as in Example 3, except that the heat treatment wasperformed by raising the temperature from room temperature (i.e., 25°C.) to 300° C. at a rate of 10° C./h and then maintaining thetemperature at 300° C. for 2 hours, and the same operations as inExample 3 were performed thereafter. The results thereof are shown inTable 1.

Comparative Example 1

A heat-treated molded body (i.e., porous molded body (1C)) was obtainedin the same manner as in Example 5, except that the crucible was notcovered with a lid and a dry air having a water vapor content of 0.27g/m³ was introduced, and the same operations as in Example 5 wereperformed thereafter. It is noted here that the average water vaporcontent during the heat treatment is estimated to be equivalent to thewater vapor content in the dry air (i.e., 0.27 g/m³).

Further, in Comparative Example 1, an α-olefin dimerization catalyst wasprepared in the same manner as in Example 1, and a dimerization reactionof propylene was performed using this α-olefin dimerization catalyst.The results thereof are shown in Table 1.

TABLE 1 Example Example Example Example Example Example Comparative 1 23 4 5 6 Example 1 Raw material of Bicarbonate compound (A) KHCO₃ 60 8080 80 80 80 70 molded body (parts by mass) Compound (B) K₂CO₃ (parts bymass) 40 20 20 20 20 20 30 Median diameter d50 (μm) 140 130 130 130 130130 120 Content ratio of particles having a particle 3.0 6.0 6.0 6.0 6.06.0 7.5 size of 40 μm or smaller (% by mass) Heat treatment Totalheating time (hr) 21 18 12 6.6 2.5 29.5 2.5 Heat treatment time 15.510.0 4.5 1.5 0.3 10.0 0.3 (thermal decomposition time) (hr) Thermaldecomposition rate of (A) (% by mass) 100 100 100 100 100 100 100Calculated value of water vapor content (g/m³) 20.6 15.2 210 to 294 210to 294 210 to 294 210 to 294 0.27 Porous molded Pore volume (mL/g) 0.210.25 0.26 0.25 0.24 0.25 0.21 body Median pore size (μm) 0.60 0.55 0.540.48 0.42 0.72 0.36 Crushing strength in radial direction (kgf) 3.4 3.94.0 4.1 3.9 4.9 7.0 Sodium support Support ratio (% by mass) 3.5 3.5 — —— — 3.5 Dimerization Propylene conversion rate (%) 21.2 21.9 — — — —21.8 reaction 4MP-1 selection rate (%) 91.7 90.9 — — — — 90.5

FIG. 1 shows the relationships between the pore size and the logdifferential pore volume in the porous molded bodies of Examples andComparative Example.

As shown in Table 1 and FIG. 1 , in all of the porous molded bodies ofExamples 1 to 6 that were each obtained by heat-treating a molded bodycontaining the bicarbonate compound (A) and the compound (B) in anatmosphere containing from 1.0 g/m³ to 750,000 g/m³ of water vapor, thepore size (i.e., median pore size) was adjusted to be larger than thatof the porous molded body of Comparative Example 1 that was obtained byheat-treating a molded body in a dry air (i.e., in an atmospherecontaining 0.27 g/m³ of water vapor). Further, it is seen that theporous molded bodies of Examples 1 to 6 are observed with a tendencythat not only the pore size but also the pore volume are adjusted to belarge.

Moreover, in the α-olefin dimerization reactions using the catalystsproduced from the porous molded bodies of Examples 1 and 2, theselectivity of 4-methyl-1-pentene (i.e., 4MP-1) was improved as comparedto the case where the catalyst produced from the porous molded body ofComparative Example 1 was used.

From these results, it is seen that the reaction selectivity in anα-olefin dimerization reaction is improved by using each of the porousmolded bodies of Examples 1 to 2, which are adjusted to have a largerpore size, as a carrier of an α-olefin dimerization catalyst.

FIG. 2 shows the relationships between the heat treatment time (i.e.,thermal decomposition time of KHCO₃) and the median pore size of therespective porous molded bodies in Examples and Comparative Example. Asshown in FIG. 2 , it is confirmed that the median pore size can beadjusted to be larger as the heat treatment time is extended. Moreover,it is confirmed that the median pore size tends to be larger as thewater vapor content during the heat treatment is increased.

The disclosure of Japanese Patent Application No. 2016-249237 filed onDec. 22, 2016, is hereby incorporated by reference in its entirety.

All the documents, patent applications and technical standards that aredescribed in the present specification are hereby incorporated byreference to the same extent as if each individual document, patentapplication or technical standard is concretely and individuallydescribed to be incorporated by reference.

The invention claimed is:
 1. A method of producing a porous molded body,the method comprising: the step of obtaining a molded body by molding araw material that contains from 1 part by mass to 100 parts by mass of abicarbonate compound (A) represented by AHCO₃ (wherein, A represents Naor K) and from 0 parts by mass to 99 parts by mass of a compound (B)represented by B_(n)X (wherein, B represents Na or K; X represents CO₃,SO₄, SiO₃, F, Cl, or Br; and n represents an integer of 1 or 2 asdetermined by the valence of X) (provided that a total amount of (A) and(B) is 100 parts by mass); and the step of obtaining a porous moldedbody by performing a heat treatment of the molded body in a temperaturerange of from 100° C. to 500° C. and an atmosphere that contains watervapor in an amount of from 1.0 g/m³ to 750,000 g/m³ and therebythermally decomposing not less than 90% by mass of the bicarbonatecompound (A).
 2. The method of producing a porous molded body accordingto claim 1, wherein the duration of the heat treatment is from 0.3 hoursto 24 hours.
 3. The method of producing a porous molded body accordingto claim 1, wherein the temperature of the heat treatment is in a rangeof from 100° C. to 300° C.
 4. The method of producing a porous moldedbody according to claim 1, wherein the heat treatment is performed in anatmosphere that contains from 10.0 g/m³ to 750,000 g/m³ of water vapor.5. The method of producing a porous molded body according to claim 1,wherein not less than 97% by mass of the bicarbonate compound (A) isthermally decomposed by the heat treatment.
 6. The method of producing aporous molded body according to claim 1, wherein, when a total amount ofthe bicarbonate compound (A) and the compound (B) in the raw material is100 parts by mass, the amount of the bicarbonate compound (A) is from 10parts by mass to 100 parts by mass and that of the compound (B) is from0 parts by mass to 90 parts by mass.
 7. The method of producing a porousmolded body according to claim 1, wherein the raw material is molded bytableting.
 8. The method of producing a porous molded body according toclaim 1, wherein, when the raw material contains the compound (B), amixture of the bicarbonate compound (A) and the compound (B) has amedian diameter (d50) of from 5 μm to 600 μm in terms of volumestatistical value, and when the raw material does not contain thecompound (B), the bicarbonate compound (A) has a median diameter (d50)of from 5 μm to 600 μm in terms of volume statistical value.
 9. Themethod of producing a porous molded body according to claim 1, wherein acontent ratio of particles having a particle size of 40 μm or smaller inthe raw material is from 3% by mass to 30% by mass.
 10. The method ofproducing a porous molded body according to claim 1, wherein thebicarbonate compound (A) is potassium bicarbonate KHCO₃).
 11. The methodof producing a porous molded body according to claim 1, wherein thecompound (B) is potassium carbonate (K₂CO₃).
 12. The method of producinga porous molded body according to claim 1, wherein the raw materialfurther contains a graphite (C).
 13. A method of producing an α-olefindimerization catalyst, the method comprising: the step of producing aporous molded body by the method of producing a porous molded bodyaccording to claim 1; and the step of obtaining an α-olefin dimerizationcatalyst by supporting an alkali metal (D) on the porous molded body.14. A method of producing an α-olefin dimer, the method comprising: thestep of producing an α-olefin dimerization catalyst by the method ofproducing an α-olefin dimerization catalyst according to claim 13; andthe step of obtaining an α-olefin dimer by performing a dimerizationreaction of an α-olefin in the presence of the α-olefin dimerizationcatalyst.